Detect monkey patching and emit a deprecation warning.

This isn't comprehensive but it should be broad enough to ensure that most
people who would be affected by blocking monkey patching see a warning.
Covers the jasmine namespace as well as classes that are monkey patched by
zone.js.

Replacing globals (describe/it/etc) doesn't trigger a warning because they
belong to the user and are expected to be replaced.

src/core/deprecateMonkeyPatching.js

@@ -0,0 +1,22 @@
+getJasmineRequireObj().deprecateMonkeyPatching = function(j$) {
+  return function deprecateMonkeyPatching(obj, keysToSkip) {
+    for (const key of Object.keys(obj)) {
+      if (!keysToSkip?.includes(key)) {
+        let value = obj[key];
+
+        Object.defineProperty(obj, key, {
+          enumerable: key in obj,
+          get() {
+            return value;
+          },
+          set(newValue) {
+            j$.getEnv().deprecated(
+              'Monkey patching detected. This is not supported and will break in a future jasmine-core release.'
+            );
+            value = newValue;
+          }
+        });
+      }
+    }
+  };
+};